Transposition and amplification of a large piece of mitochondrial (mt) DNA in a nuclear chromosome in feline species were characterized as an approach to determining the molecular aspects of gene transposition, gene amplification and mtDNA evolution. Molecular characterization of both nuclear and cytoplasmic mtDNA clones revealed that (i) the nuclear mtDNA contains approximately one-half of the intact mt genome; (ii) this mtDNA fragment is amplified tandemly 38-76 times on a centromeric region of chromosome D2; (iii) a magnitude of amplification differs in each allele, suggesting active expansion and contraction of these repeats; (iv) d(CA) repeat sequences found at 5' and 3' ends of the nuclear mtDNA sequence may be responsible for these transpositions and amplifications; and (v) dating of transposition and integration of this genome into a single chromosome D2, was estimated to be 1.8-2.0 million years ago in an ancestral species of the domestic cat.